Yards from the Houses of Parliament, the 'IoS' conference on the decriminalisation of the drug draws 700
"It's easy to see why it's called dope," declared the leaflet, bravely. "Only a dope would be stupid enough to use it, and only a stupidly corrupt or criminal person would try and get their 'friends' to also use it." It was a valiant attempt at disinformation, published under the copyright of someone calling themselves E Kenneth Eckersley CMS, HSDC, FIOD, FIMgt, FISMM, MCIM, HonMPHMA (Int). But, distributed to delegates of an open debate on the decriminalisation of cannabis, held by the Independent on Sunday on Thursday, its message largely fell on deaf ears.

The event, at the Queen Elizabeth II Conference Centre "a stone's throw from the Mother of Parliaments", brought together 700 people - the washed and the unwashed, Christians and weed-worshippers, delegates wearing head- to-toe hemp and Armani-clad politicians - under the heading "Cannabis: Should It Be Decriminalised?". And as the platform speakers began their speeches under the gentle chairmanship of Channel 4's Jon Snow, the debate also spilled over on to the conference floor.

After this newspaper's editor, Rosie Boycott, and Professor John Strang, a director of the National Addiction Centre, had opened the debate, Barry Clark, who has multiple sclerosis, was first on his feet. "A few years ago I was told that I had three years before I ended up in a wheelchair," he said. "But my neurologist, doctor and pain therapist all told me to take cannabis and I'm still walking today." He looked puzzled. "I have got to be a criminal to grow and take cannabis. I just want to know why I can't smoke it in my own home."

The Labour MP Austin Mitchell declared himself open-minded on the subject. "I'm here to exhale rather than to inhale," he told delegates. On behalf of the Alliance for Cannabis Therapy, he had last week approached the Home Office to discuss making the drug available on prescription, but he had been told there was "no political will". He was confused because the reason the Home Office gave was that there was no research - yet it was also refusing to commission any.

"Meanwhile, thousands of MS sufferers are being forced into the backstreets, into illegality," he said. The comparable prescription drug, Nabilone, was addictive and had serious side-effects, where cannabis did not. "The law is coming into disrepute," said Mr Mitchell. "It is absolutely wrong that MS sufferers should be treated in this way."

A psychiatric nurse in the audience wanted to know when prison governors were going to be locked up, given that knowingly permitting a person to smoke cannabis on your premises carries a heavy sentence.

Then a man, who introduced himself as Dr Franklin, declared he had bad news for the conference. Cannabis was unhelpful for Parkinson's disease and, indeed, made it worse, he said to a chorus of disagreement. "It does work," said another member of the audience who suffered with the disease. "It's not a cure, but it alleviates the condition and helps you sleep. The first time I smoked it, I woke up and wondered if I'd got my old legs back." He shook his head sadly. "It was only for a couple of minutes, but it was absolutely worth it."

The Body Shop founder, Anita Roddick, spoke of a need for compassionate law-making, and a man wearing a suit declared he had used cannabis for 20 years and still held down a responsible job. The Conservative MP Barry Evans urged the conference to count the human cost of decriminalisation. Psychiatric hospitals were full of patients who had smoked large amounts of strong cannabis, he said.

He then became entangled in a long metaphor about "unscrambling eggs". Alcohol and cigarettes, he said, were eggs already scrambled, but it wasn't too late for cannabis which was still unscrambled. There was also the problem of unscrambling the medical-marijuana question from the recreational- use issue. People at the front claimed he was talking like a dopehead. Mr Evans said he was used to voicing unpopular views. "After all, I am a Welsh Tory," he said, to applause.

A member of the audience wanted to know whether Cow and Gate babyfoods were a "gateway drug" - a substance which leads to harder drug use. After all, some people who had used C&G had ended up on heroin. Another woman was concerned about the dangers of Cocopops, which young people were attracted to because they tasted nice. It may have been that she thought they might lead to harder cereals, like bran flakes. Or, perhaps she meant Alcopops.

The handsome Italian MEP Gianfranco Dell'Alba took the audience by surprise by declaring himself in favour of legalising, not decriminalising cannabis. And why stop there? "Legalise all drugs!" he cried, standing at the podium in his Armani suit. One or two activists were seen to swoon, although that could have been the effect of a large basket of hash-brownies, slowly making its way through the audience.

"I'm Dutch and I don't think the policy in the Netherlands works," declared a woman in leather trousers - only to be interrupted by someone also claiming to be Dutch who thought decriminalisation worked. "No, I'm Dutch!" shouted the first woman. In the end they agreed they were both from the Netherlands.

Mike Goodman, director of the drugs charity Release, explained that more people had died playing association football than from using cannabis. The exact score was 98 to the footballers and nil to the cannabis users. At the current rate of arrest, a million people would have been charged with cannabis-related offences by the millennium, he said.

He paraphrased the philosopher John Stuart Mill: "People should have the right to have control over their own lives, provided they do not harm anybody else." Mr Goodman welcomed any move to decriminalise cannabis - and called for a watchdog, Ofpot, to be established to act as a quality- control agency. "I think a lot of people would volunteer for a seat on that agency," he said to cheers.

Dressed entirely in hemp clothing, a young man who had changed his name by deed poll to Free Rob Cannabis, said he would shortly begin a jail sentence for possessing cannabis. He was looking for sponsors for each day he was in jail. The money would go to his charity, the Free Medical Marijuana Foundation, which supplied cannabis to Multiple Sclerosis, chemotherapy and glaucoma patients free of charge.

Professor Colin Blakemore, more usually at odds with the green activist contingent of the audience as an advocate of animal experimentation, drew applause from the crowd with his support for the Netherlands' policy. It had proved useful in "decoupling hard and soft drugs", he said. In the Netherlands, 2 per cent of the population had used cocaine, while in the US it was 33 per cent. "The decriminalisation of cannabis would be a sign not of weakness but of political maturity for this government, in which we have so much hope." He suggested that the Independent on Sunday should ask Formula One to sponsor its campaign.

David Partington, of the Evangelical Coalition on Drugs, compared his role at the conference to that of Christians entering the arena in Roman times. "We're still going strong after 2,000 years," he said. But he seemed to sense the approach of Armageddon, "when pleasure and instant gratification become the determining feature of [society's] conscience at the expense of the individual."

Mr Partington had recently met a man with a son, whom he would call James, who had nearly died from a "cannabis overdose". "There are thousands and thousands of Jameses outside the sophisticated building that is the Queen Elizabeth Conference Centre," he said. Inside the sophisticated building an unmistakable smell was already wafting from the traditional direction of the back row, despite the QEII conference centre's firm no-smoking policy.

"Just because you're paranoid doesn't mean they aren't out to get you," said Mr Partington, noting that his slides had somehow got rather jumbled up.

Lynn Zimmer, an associate of the Soros Foundation and co-author of Marijuana Myths, Marijuana Facts, invited the audience to forget all about the weed for a minute and think about sex. We were to imagine a married man and a married woman spending a night of passion in a hotel room. What they were doing had the potential to cause hurt to both the couple and their families, and in many people's eyes it was "immoral, wrong, harmful". "Should adultery be made illegal?" she asked. Should the government declare a war on adultery and on flirting, the gateway to adultery?

As Mr Snow drew the conference to a close delegates lined up by Free Rob Cannabis to explain they were suffering from a range of illnesses and could they please get on his free-cannabis mailing list? A few people said the debate had changed their minds. "I would never have been seen dead at a place like this a year ago," said one man, looking ill at ease, "but since my son went to prison for possessing a tiny amount of cannabis, I've decided to do my bit."